From f6084d4af5f159f013d36262a7f15262210b4879 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Fri, 20 Dec 2024 22:16:12 +0100
Subject: [PATCH] =?UTF-8?q?java:=20add=20=C2=AB2415.=20Reverse=20Odd=20Lev?=
 =?UTF-8?q?els=20of=20Binary=20Tree=C2=BB?=
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URL:	https://leetcode.com/problems/reverse-odd-levels-of-binary-tree/
---
 java/reverse-odd-levels-of-binary-tree.java | 39 +++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 java/reverse-odd-levels-of-binary-tree.java

diff --git a/java/reverse-odd-levels-of-binary-tree.java b/java/reverse-odd-levels-of-binary-tree.java
new file mode 100644
index 0000000..da5519e
--- /dev/null
+++ b/java/reverse-odd-levels-of-binary-tree.java
@@ -0,0 +1,39 @@
+class Solution {
+  private void traverse(ArrayList<ArrayList<TreeNode>> nodes, int level, TreeNode node) {
+    if (node == null) {
+      return;
+    }
+
+    if (level % 2 == 1) {
+      var idx = level >> 1;
+      while (nodes.size() <= idx) {
+        nodes.addLast(new ArrayList<TreeNode>());
+      }
+
+      nodes.get(idx).addLast(node);
+    }
+
+    traverse(nodes, level + 1, node.left);
+    traverse(nodes, level + 1, node.right);
+  }
+
+  private void reverse(ArrayList<TreeNode> level) {
+    int i, j;
+    for (i = 0, j = level.size() - 1; i < j; ++i, --j) {
+      var tmp = level.get(i).val;
+      level.get(i).val = level.get(j).val;
+      level.get(j).val = tmp;
+    }
+  }
+
+  public TreeNode reverseOddLevels(TreeNode root) {
+    var nodes = new ArrayList<ArrayList<TreeNode>>();
+    traverse(nodes, 0, root);
+
+    for (var level : nodes) {
+      reverse(level);
+    }
+
+    return root;
+  }
+}